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Biomedical subjects

D J Dawson

Publications and source records attributed to D J Dawson.

At least 19 recordsLinked to original sources
PubMed2002

Biocide use in the food industry and the disinfectant resistance of persistent strains of Listeria monocytogenes and Escherichia coli.

AIMS: The aims of the project were threefold: to survey the use of disinfectants in the UK food industry; to assess the product and environmental microflora of selected food factories for the persistence of Listeria monocytogenes and Escherichia coli; and to determine the disinfectant resistance of any persistent strains. METHODS AND RESULTS: A survey of the use of disinfectants in the UK food industry was undertaken in which a total of 40 sites were visited and a further 77 postal questionnaires were returned from farms, food manufacture, food transport and food retail sites. Quaternary ammonium compounds (QACs) were predominantly used, applied in small volumes as a mist. Approximately 30,000 samples from the product and environment of five chilled food factories were examined for L. monocytogenes and E. coli over a 3 year period. A total of 181 L. monocytogenes and 176 E. coli isolates were ribotyped to yield 19 and 34 ribogroups, respectively. Some strains were isolated only from the product, a number only from the environment and others from both niches. Some strains were seen to be persistent for the duration of the sampling exercise (2-3 years). The most common L. monocytogenes and E. coli strains, together with two environmental L. monocytogenes strains, were assessed for any resistance to commercial disinfectants as compared with a laboratory L. monocytogenes disinfectant testing strain. The resistance of the L. monocytogenes and E. coli strains isolated from the factory were not significantly different from the laboratory control strain. CONCLUSIONS: Persistent strains of L. monocytogenes and E. coli are found in the UK food industry, though this persistence is not related to their increased susceptibility to the most commonly used disinfectants. SIGNIFICANCE AND IMPACT OF THE STUDY: The concept of a persistent microflora in food factories will have an impact on the future selection of suitable control options, including the use of biocides.

DNA Fingerprinting↗
PubMed2002

Biocide use in the food industry and the disinfectant resistance of persistent strains of Listeria monocytogenes and Escherichia coli.

AIMS: The aims of the project were threefold: to survey the use of disinfectants in the UK food industry; to assess the product and environmental microflora of selected food factories for the persistence of Listeria monocytogenes and Escherichia coli; and to determine the disinfectant resistance of any persistent strains. METHODS AND RESULTS: A survey of the use of disinfectants in the UK food industry was undertaken in which a total of 40 sites were visited and a further 77 postal questionnaires were returned from farms, food manufacture, food transport and food retail sites. Quaternary ammonium compounds (QACs) were predominantly used, applied in small volumes as a mist. Approximately 30,000 samples from the product and environment of five chilled food factories were examined for L. monocytogenes and E. coli over a 3 year period. A total of 181 L. monocytogenes and 176 E. coli isolates were ribotyped to yield 19 and 34 ribogroups, respectively. Some strains were isolated only from the product, a number only from the environment and others from both niches. Some strains were seen to be persistent for the duration of the sampling exercise (2-3 years). The most common L. monocytogenes and E. coli strains, together with two environmental L. monocytogenes strains, were assessed for any resistance to commercial disinfectants as compared with a laboratory L. monocytogenes disinfectant testing strain. The resistance of the L. monocytogenes and E. coli strains isolated from the factory were not significantly different from the laboratory control strain. CONCLUSIONS: Persistent strains of L. monocytogenes and E. coli are found in the UK food industry, though this persistence is not related to their increased susceptibility to the most commonly used disinfectants. SIGNIFICANCE AND IMPACT OF THE STUDY: The concept of a persistent microflora in food factories will have an impact on the future selection of suitable control options, including the use of biocides.

Anti-Bacterial Agents↗
PubMed2000

Microbiological safety of water.

Significant advances in water treatment over the last century have resulted in massive improvements in the microbiological safety of public drinking water supplies in the UK and the developed countries. Incidences of illness due to poor treatment or post-treatment contamination are rare, but when they occur tend to attract considerable media attention. A well managed water treatment works and supply system can provide high quality drinking water wherever in the world it is located. As a rule, throughout the world, private supplies tend to be of a poorer quality than public supplies, but poorly managed public supplies have the potential to make a large number of people ill and continued effort is needed to maintain and improve drinking water quality world-wide.

Bacteria↗
PubMed1999

Tuberculosis due to Mycobacterium bovis in the Australian population: cases recorded during 1970-1994.

OBJECTIVE: To determine the contribution of Mycobacterium bovis to active tuberculosis in the Australian population during 1970-1994, and to collate and analyse demographic data from bacteriologically proven cases. DESIGN: Summary data for tuberculosis cases notified by Australian public health agencies during 1970-1985 and 1991-1994 were obtained from the database of notifiable diseases maintained by the Department of Health and Family Services. More detailed demographic data for cases confirmed by bacteriology during 1970-1994 were supplied by the Australian Mycobacterium Reference Laboratory Network. RESULTS: At least 236 cases of bovine tuberculosis (TB) occurred in the Australian population during 1970-1994 (mean 9.4 cases; range 3-22 cases annually). The bovine strain has accounted for around 1% of Australian cases of TB during this period. Laboratory sources provided demographic data for 150 cases with positive bacteriology. For this group, the mean age was 54 years (range 22-86), and the male:female ratio was 2.4:1. The majority of cases (74%) involved pulmonary disease. Australian-born persons accounted for 68% of the total cases and typically had histories of employment in meat and/or livestock industries. CONCLUSION: M. bovis was responsible for less than 1.5% of cases of TB in the Australian population during 1970-1994. Most cases were apparently due to reactivation of infection acquired through occupational exposure. Thus, although virtual eradication of M. bovis from Australia's cattle herds has now reduced the risk of exposure, it can be expected that human cases of bovine TB will continue to be detected for years to come. The bovine strain should be considered as the possible agent of TB in foreign-born Australians.

Adult↗
PubMed1999

Tuberculosis due to Mycobacterium bovis in the Australian population: DNA typing of isolates, 1970-1994.

SETTING: Bacteriologically confirmed cases of Mycobacterium bovis in the Australian population. OBJECTIVE: To evaluate the DNA fingerprinting techniques commonly used for M. bovis on isolates from humans and determine whether they were useful for determining the origin of human infection. DESIGN: M. bovis strains isolated between 1970 and 1994 were obtained from five Australian Reference Laboratories. Four DNA fingerprinting techniques, comprising Southern hybridisation with three different probes (the insertion sequence [IS]6110, the polymorphic guanine-cytosine-rich sequence [PGRS] and the direct repeat [DR]) and a PCR-based method (spoligotyping) were used. RESULTS: The PGRS, DR and IS6110 RFLP methods identified 32, 22 and 14 different types respectively from the 45 isolates available. Spoligotyping identified 18 different types. When all methods were combined 41 different strains were identified. Clear differences were found between many isolates from Australian-born patients and those from patients born overseas. CONCLUSIONS: The PGRS RFLP method was the most effective method for typing the human strains, but a combination of methods is recommended for maximum sensitivity. Most Australian-born patients that had worked in the meat and livestock industries were infected with strains similar to those that are commonly found in Australian cattle, confirming the occupational risk in these industries. Patients born overseas were typically infected with strains genetically different from those of patients born in Australia. This suggests that patients born overseas identified with M. bovis were presenting with reactivation of infection acquired outside Australia.

Adult↗
PubMed1998

Subcutaneous granuloma caused by Mycobacterium avium complex infection in a cat.

A localised subcutaneous swelling developed on the nasal bridge of a cat receiving chemotherapy for alimentary tract lymphosarcoma. Cytological and histological examination of representative samples of the lesion demonstrated pyogranulomatous inflammation and abundant acid-fast bacilli. A Mycobacterium sp was cultured from tissue excised from the lesion. Extensive testing at three reference laboratories indicated the strain was a member of the Mycobacterium avium complex. The infection was treated successfully by cytoreductive surgery and a 6 weeks course of orally administered clofazimine.

Animals↗
PubMed1998

A doorless entry system for high-energy radiation therapy rooms.

A doorless entry system has been designed for use in high-energy radiation therapy rooms. The doorless entry improves patient access, safety and throughput, increases the physical safety for the radiation therapists, and avoids the significant cost of heavy shielding doors. The design meets concerns relating to radiation safety, operational ease, and authorized entry. The new system is currently operating in one room housing a cobalt-60 unit and is to be employed in five additional rooms housing dual-energy accelerators (maximum energies of 10 and 18 MV). The doorless entry has received wide approval from the radiation therapists and no concerns have been expressed with respect to unauthorized entry or radiation safety.

Biomedical Engineering↗
PubMed1997

Characterization of Mycobacterium avium complex related mycobacteria isolated from an African environment and patients with AIDS.

Thirteen isolates from African AIDS patients and from the environment in Zaire were identified as members of the Mycobacterium avium complex by phenotypic tests. RFLP analysis showed that the isolates belong to a genetically homogeneous cluster. The 16S rRNA sequence analysis suggests a close relationship with the P-49 strain (ATCC 35847), a reference strain for the serotype 7 of M. avium complex. This work shows the close relationship between certain M. avium complex strains responsible for disseminated infection in AIDS patients and M. avium complex strains isolated from the environment in Zaire. Further, our findings confirm that atypical mycobacteria may disseminate in AIDS patients in Africa and suggest that infection in these patients probably originates in their environment.

AIDS-Related Opportunistic Infections↗
PubMed1995

Tuberculosis in Australia, 1989-1992. Bacteriologically confirmed cases and drug resistance.

OBJECTIVE: To collate statistics, including drug susceptibility, of patients with bacteriologically confirmed tuberculosis in Australia during 1989-1992. DESIGN: Collaborative project among the five Australian mycobacterial reference laboratories. STUDY POPULATION: 2509 Australian residents with bacteriologically confirmed tuberculosis. OUTCOME MEASURES: Patient and specimen data, and drug susceptibility results recorded for isolates of Mycobacterium tuberculosis and Mycobacterium bovis. RESULTS: The annual incidence during 1989-1992 was about 3.6 per 100,000. The male-to-female ratio was 1.4:1 and about half the patients were under 50. Older men had high rates of disease. Lymphatic disease was significantly more common in females; the converse was true for pulmonary and pleural disease. Resistance to at least one of the common antituberculosis drugs was detected in 14.4% of isolates, and usually involved streptomycin (7.6%) and isoniazid (8.4%). Fewer than 1% of isolates were resistant to isoniazid and rifampicin in combination. CONCLUSIONS: By international standards, Australia remains a "low-incidence" country for tuberculosis, with a static annual incidence. Multiple drug resistance is uncommon and most patients should respond to the standard four-drug regimen. Nevertheless, because clinical data confirm that the pool of infected persons is being supplemented through immigration, and that certain population subgroups have high rates of disease, it is essential that Australia maintain effective control programs.

AIDS-Related Opportunistic Infections↗
PubMed1995

Mycobacterium asiaticum as the probable causative agent in a case of olecranon bursitis.

Mycobacterium asiaticum was isolated from fluid aspirated from an olecranon bursa that had become inflamed following a superficial injury. Other possible causes of the inflammation were excluded. No specific antimycobacterial therapy was given. The infection responded to drainage, regular dressing, and immobilization. Our experience suggests that M. asiaticum is a potential cause of infection of the joints and surrounding tissues.

Adult↗
PubMed1993

Identification of Mycobacterium avium complex strains belonging to serovars 21-28 by three commercial DNA probe tests.

Various reference strains of Mycobacterium avium complex (MAC) belonging to serovars 21-28 were identified by three DNA probe tests, i.e., Gen-Probe, AccuProbe and SNAP tests. All of these DNA probe tests were in agreement for strains identified as M. avium or M. intracellulare. The tested serovar strains involved M. avium, M. intracellulare, MAC reactive only with Probe X of SNAP test ('Probe X-reactive MAC'), M. scrofulaceum reactive with Probe X of SNAP test ('Probe X-reactive M. scrofulaceum'), and typical M. scrofulaceum which did not react with any of the probes. Both reference strains belonging to serovar 21 were M. avium, and none of the other serovars included this species. On the contrary, M. intracellulare was found in serovars 22, 25, 26, and 28. 'Probe X-reactive MAC' were also widely found in serovars 23, 24, 26, 27, and 28, while 'Probe X-reactive M. scrofulaceum' was seen only in serovar 22. These results confirm the usefulness of SNAP test to identify the MAC showing no reactivity to Gen-Probe and AccuProbe.

DNA Probes↗
PubMed1993

Comparison of the virulence for mice of Mycobacterium avium and Mycobacterium intracellulare identified by DNA probe test.

The virulence of various serovars of Mycobacterium avium and M. intracellulare identified by DNA probe test was compared with each other. We found species- and serovar-dependencies of M. avium complex (MAC) virulence to mice in terms of mortality, incidence of lung lesions and bacterial load in the visceral organs, as follows. First, human- or environment-derived M. intracellulare was more virulent for mice, as compared to M. avium isolated from patients or environmental sources. Second, the virulence of MAC isolates belonging to serovars 1, 8, 9 (M. avium), 14 and 16 (M. intracellulare) is in the order of serovars 16 > 14 > 8 > 1 > 9. These aspects were different from those for MAC virulence to human and bird, swine and cattle.

Animals↗
PubMed1993

Biochemical properties and fatty acid composition of Mycobacterium haemophilum: study of 16 isolates from Australian patients.

The biochemical properties and fatty acid compositions of 16 strains of Mycobacterium haemophilum from Australian patients were studied. The strains proved to be indistinguishable from each other but could readily be differentiated from other slowly growing mycobacteria with similar cultural features. Mycolic acid analyses revealed the presence of alpha-, methoxy-, and ketomycolates. The fatty acid composition supports the validity of the fact that M. haemophilum is a distinct species. The fatty acid composition was consistent among the 16 strains, but it was unusual in that there was some resemblance to the fatty acid composition of M. leprae. The wide range of pHs (5.4 to 7.4) that supported growth of M. haemophilum on artificial medium is in keeping with suggestions that M. haemophilum exists in an environmental habitat.

Australia↗
PubMed1992

Mycobacterium haemophilum causing perihilar or cervical lymphadenitis in healthy children.

We describe five apparently immunologically normal children with infection caused by Mycobacterium haemophilum and resulting in perihilar or cervical lymphadenitis. Clinical distinction from Mycobacterium tuberculosis infection could be made by culture only, because differential Mantoux test results suggested tuberculosis. Treatment of these children involved chemotherapy or surgery or both, and outcome in all cases has been excellent. We believe that M. haemophilum should be added to the list of non-tuberculosis mycobacteria known to cause lymphadenitis in otherwise healthy children.

Antitubercular Agents↗